The biggest one is that the parking lots at the nearby ones are CRAZY. Always packed, and even worse on weekends. They are so bad, in fact, that I even avoid the streets NEAR the Costco, because they back up. And I live in Los Angeles, where I expect bad parking and traffic... this is another level.
Also, I am just getting so used to ordering everything online. We get all our household items via amazon subscriptions (toilet paper, paper towels, dish detergent, etc)... so nice not having to ever think about those things and they just show up when we need them. I can't see myself going back to shopping at stores myself for those things.